X-ray reduction system

ABSTRACT

This invention relates to a multiple frame imaging system including radiation source, a detector having an input area, a monitor configured to display detected images, means for determining at least one Region of Interest (ROI) of an object on the displayed image, and a collimator having means for projecting the at least one region of interest (ROI) on at least one selected fraction of the input area exposed by the x-ray source. The collimator including at least three essentially non-overlapping plates mounted in a plane generally parallel to the detector input surface plane, each plate includes a first edge in contact with an edge of a first neighboring plate and a second edge adjacent to the first edge in contact with an edge of a second neighboring plate; and means for moving each one of the plates.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is the U.S. National Phase of PCT ApplicationNo. PCT/IB/2014/065661 filed 20 Oct. 2014 which claims priority from andis related to U.S. Provisional Patent Application Ser. No 61/914,405,filed 11 Dec 2013, and to U.S. Provisional Patent Application Ser. No.61/927,504, filed 15 Jan. 2014, each of which are incorporated byreference in its entirety herein.

FIELD OF THE INVENTION

The invention is related to the field of x-ray imaging and moreparticularly to the field of controlling x-ray radiation amount duringmultiple frames imaging.

BACKGROUND OF THE INVENTION

In a typical multiple frames imaging (MFI) system the x-ray tubegenerates x-ray radiation over a relatively wide solid angle. To avoidunnecessary exposure to both the patient and the medical team,collimators of x-ray absorbing materials such as lead are used to blockthe redundant radiation. This way only the necessary solid angle ofuseful radiation exits the x-ray tube to expose only the necessaryelements.

Such collimators are used typically in a static mode but may assume avariety of designs and x-ray radiation geometries. Collimators can beset up manually or automatically using as input, for example, thedimensions of the organ environment that is involved in the procedure.

In multiple frames imaging, where typically a series of images are takenautomatically one after the other, the situation is more dynamic than ina single exposure x-ray.

For such cases collimators with materials partially-transparent to x-raymay be used to manipulate the x-ray energy distribution.

It is desired to change the distribution of the x-ray energy during theMFI session so that for at least 2 different frames of the MFI sessionthe distribution of the x-ray beam will be different.

In MFI the x-ray radiation is active for a relatively long period andthe treating physician typically has to stand near the patient,therefore near the x-ray radiation. As a result, it is desired toprovide methods to minimize exposure to the medical team. Methods forreducing x-ray radiation intensity have been suggested where theresultant reduced signal to noise ratio (S/N) of the x-ray image iscompensated by digital image enhancement. Other methods suggest acollimator limiting the solid angle of the x-ray radiation to a fractionof the image intensifier area and periodically moving the collimator toexpose the entire input area of the image intensifier so that the Regionof Interest (ROI) is exposed more than the rest of the area. This way,the ROI receives high enough x-ray radiation to generate a good S/Nimage while the rest of the image is exposed with low x-ray intensity,providing a relatively low S/N image or reduced real-time imaging, asper the collimator and method used. The ROI size and position can bedetermined in a plurality of methods. For example, it can be a fixedarea in the center of the image or it can be centered automaticallyabout the most active area in the image, this activity is determined bytemporal image analysis of sequence of cine images received from thevideo camera of the multiple frames imaging system.

It is desired to provide collimator solutions to enable reduction ofdose during MFI.

It is also desired to provide a method to move the collimator elementsso as to support best imaging results.

It is desired to provide a method to handle the effects of this motionon image quality.

A SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided amultiple frame imaging system comprising: an x-ray source; a detectorhaving an input area; a monitor configured to display detected images;means for determining the location of at least one Region of Interest(ROI) of a patient on the displayed image; and a collimator comprisingmeans for projecting the at least one region of interest (ROI) on atleast one selected fraction of the input area exposed by the x-raysource, the collimator comprising at least three essentiallynon-overlapping plates mounted in a plane generally parallel to thedetector input surface plane, wherein each plate comprises a first edgein contact with an edge of a first neighboring plate and a second edgeadjacent to the first edge in contact with an edge of a secondneighboring plate; and means for moving each one of the plates in theplane.

One of the plates may be opaque or partially transparent to x-rayradiation and the positioning of the plates may be configured to createa fully transparent area in a gap formed by the essentiallynon-overlapping plates, for projecting the at least one region ofinterest (ROI) and a second opaque or partially transparent areascovered by the plates.

The plates may be movable in perpendicular directions.

Each one of said plates may be connected to a carriage movable by atleast one motor and a transmission system along a track.

The at least one motor may comprise a single motor and each one of theplates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via thecoupler.

The at least one motor may comprise two motors configured to move theplate in perpendicular directions.

The plates' edges may have a profile selected from the group consistingof: straight, V-shaped and tapered.

The system may further comprise: an image processing unit connectedbetween the detector and the monitor, the image processing unitconfigured to optimize the detected image displayed on the monitoraccording to at least one image parts in the at least one ROI.

The image optimization may comprise determining a tone reproductionfunction for the image.

The tone reproduction function may be implemented as one of a brightnessfunction, a contrast function, a gamma function, an offset function, ann-degree linear function and a non-linear function.

The image optimization may comprise controlling the x-ray sourceparameters.

The x-ray source parameters may be selected from the group consistingof: current mode, Peak Kilo Voltage (PKV), pulse length and AutomaticGain Control (AGC).

The collimator may be configured to move in accordance to the zoomsetting of the detector and the determined ROI.

According to another aspect of the present invention there is provided acollimator comprising: means for projecting at least one region ofinterest (ROI) on at least one selected fraction of an input areaexposed by an x-ray source, a collimator comprising at least threeessentially non-overlapping plates mounted in a plane generally parallelto a detector input surface plane, wherein each plate comprises a firstedge in contact with an edge of a first neighboring plate and a secondedge adjacent to the first edge in contact with an edge of a secondneighboring plate; and means for moving each one of the plates in theplane. Each one of the plates may be opaque or partially transparent tox-ray radiation and the positioning of the plates may be configured tocreate a fully transparent area in a gap formed by the essentiallynon-overlapping plates, for projecting the at least one region ofinterest (ROI) and a second opaque or partially transparent area coveredby the plates.

The plates may be movable in perpendicular directions.

Each one of the plates may be connected to a carriage movable by atleast one motor and a transmission system along a track.

The at least one motor may comprise a single motor and wherein each oneof the plates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via thecoupler.

The at least one motor may comprise two motors configured to move theplate in perpendicular directions.

The plates' edges may have a profile selected from the group consistingof: straight, V-shaped and tapered.

According to another aspect of the present invention there is provided amethod of controlling a display size of a ROI in an image of an x-rayirradiated area, comprising: providing a multiple frame imaging systemcomprising: an x-ray source; a detector having an input area; and acollimator comprising means for projecting at least one region ofinterest (ROI) on a selected fraction of the input area exposed by thex-ray source; the collimator comprising at least three essentiallynon-overlapping plates mounted in a plane generally parallel to thedetector input surface plane, wherein each plate comprises a first edgein contact with an edge of a first neighboring plate and a second edgeadjacent to the first edge in contact with an edge of a secondneighboring plate; and determining location and size of an exposed areaimage on the detector input area by moving at least one of the plates inthe plane to form a fully transparent gap between the plates.

Each one of the plates may be opaque or partially transparent to x-rayradiation and the positioning of the plates may be configured to createa fully transparent area in a gap formed by the essentiallynon-overlapping plates, for projecting the at least one region ofinterest (ROI) and a second opaque or partially transparent areascovered by the plates.

The plates may be movable in perpendicular directions.

Each one of the plates may be connected to a carriage movable by atleast one motor and a transmission system along a track.

The at least one motor may comprise a single motor and wherein each oneof the plates may be connected to an adjacent plate by a coupler.

Each one of the plates may be movable by an adjacent plate via thecoupler.

The at least one motor my comprise two motors configured to move theplate in perpendicular directions.

The plates' edges may have a profile selected from the group consistingof: straight, V-shaped and tapered.

According to another aspect of the present invention there is provided asystem for determining the shape and location of at least one Region ofInterest (ROI) comprise GUI (Graphical User Interface) means.

The GUI means may comprise means for displaying the detected images andmeans for determining the at least one ROI size, location andorientation.

The means for determining the at least one ROI size and location maycomprise sliders.

The GUI means may comprise means for displaying the detected images andmeans for determining the at least one ROI size, shape and location.

The means for determining may comprise drawing tools configured to markan enclosing shape around the at least one ROI.

According to another aspect of the present invention there is provided amethod comprising using GUI means for determining the shape and locationof at least one Region of Interest (ROI).

The GUI means may comprises displaying the detected images anddetermining the at least one ROI size, location and orientation.

Determining the at least one ROI size and location may comprise movingsliders. The GUI means may comprise displaying the detected images anddetermining the at least one ROI size, shape and location.

Determining may comprise drawing enclosing shape around the at least oneROI. According to another aspect of the present invention there isprovided a multiple frame imaging system comprising: a radiation source;a detector having an input area; a monitor configured to displaydetected images; means for determining at least one Region of Interest(ROI) of an object on a displayed image; a first collimator; a secondcollimator mounted between said first collimator and said object; aradiation controller configured to control said radiation source; and asecond collimator controller.

The radiation source may comprise an x-ray source.

The monitor may be configured to display detected images obtainedthrough at least one of said first and second collimators.

The system may further comprise connection means configured to connectsaid first collimator with said second collimator.

The connection means may comprise a mechanical connector connected toone of the c-arm, the original collimator cover, the radiation tubecover, the c-arm cabinet and a plate with wheels mounted on the floor.

The system may further comprise a robotic arm configured to drive saidsecond collimator.

The robotic arm may be directed by sensors configure to ensure that saidsecond collimator is mounted in coordination with said first collimator.

The system may further comprise a first collimator controller and arobotic arm controller.

The first collimator controller may be connected with said robotic armcontroller and is configured to direct said robotic arm.

The means for determining may comprise one of a joy stick, a keyboardand a touch screen.

The system may further comprise a rotary motor configured to enable theplate to rotate in a plane generally parallel to the detector inputsurface plane.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood in reference to the followingFigures:

FIG. 1A is a simplified schematic illustration of an exemplary layout ofa multiple frames imaging clinical environment and system;

FIG. 1B is an illustration of an exemplary layout of the system of FIG.1A showing additional details of components of the system example of theinvention;

FIG. 2 is a schematic illustration of an exemplary image displayed on amonitor of a multiple frames imaging system;

FIG. 3 is a simplified schematic illustration of an exemplary layout ofa multiple frames imaging clinical environment and system with theaddition of an input device;

FIG. 4 is a top view of a collimator constructed of four partially x-raytransparent essentially non-overlapping plates with the ROI at thecenter;

FIG. 4.1 shows an example of possible arrangement of nut 4501E;

FIG. 4A is a top view of the collimator of FIG. 4 with the ROI at anoff-center location;

FIG. 5 illustrates the x-ray intensity distribution in different areasof the image when the ROI is at the center;

FIG. 6 is a top view of another example of a collimator constructed offour partially x-ray transparent essentially non-overlapping plates withthe ROI at the center;

FIG. 6A is a top view of the collimator of FIG. 6 with the ROI at anoff-center location;

FIG. 7 is a top view of another example of a collimator constructed offour x-ray partially transparent essentially non-overlapping plates withthe ROI at the center;

FIG. 7A is a top view of the collimator of FIG. 7 with the ROI at anoff-center location;

FIG. 8 is a top view of another example of a collimator constructed ofthree x-ray partially transparent essentially non-overlapping plateswith the ROI at the center;

FIG. 8A is a top view of the collimator of FIG. 8 with the ROI at anoff-center location;

FIG. 9 is a top view of another example of a collimator constructed offive x-ray partially transparent essentially non-overlapping plates withthe ROI at the center;

FIG. 9A is a top view of the collimator of FIG. 9 with the ROI at anoff-center location;

FIG. 9B is a top view of the collimator of FIG. 9 with a different ROIat the center;

FIG. 9C is a top view of the collimator of FIG. 9 with a different ROIat the center;

FIG. 10 is a top view of another example of a collimator constructed oftwelve x-ray partially transparent essentially non-overlapping plateswith the ROI at the center;

FIG. 10A is a top view of an enlargement of the components of themotorizing elements of the collimator of FIG. 10;

FIG. 10B is a top view of the collimator of FIG. 10 with the ROI at anoff-center location;

FIG. 10C is a top view of the collimator of FIG. 10 with the ROI at thecenter;

FIG. 11 is a top view of a collimator constructed of four x-raypartially transparent essentially non-overlapping plates with the ROI atan off-center location;

FIG. 11A is a top view of the collimator of FIG. 11 with the ROI at thecenter;

FIG. 12A demonstrates the use of “straight edge” plates and theresulting image with the x-ray radiation penetration;

FIG. 12B demonstrates the use of “V shaped edge” plates and theresulting image;

FIG. 12C demonstrates the use of “tapered edge” plates and the resultingimage;

FIG. 12D demonstrates coupling when two filters are not at the samedistance from the radiation source;

FIG. 12E also demonstrates coupling when two filters are not at the samedistance from the radiation source;

FIG. 13 shows an exemplary user interface which may be implemented aspart of a control application;

FIG. 13A is another example of a user interface and automatic ROI setup;

FIG. 13B is another example of possible shape drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 13C is another example of possible shapes drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 13D is another example of possible shapes drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 13E is another example of possible shapes drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 13F is another example of possible shapes drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 13G is another example of possible shapes drawing and automatic ROIsetup using the user interface of FIG. 13A;

FIG. 14 depicts schematically an existing system with the additionalcollimator that is mechanically connected;

FIG. 15 depicts schematically an existing system with the additionalcollimator that is driven by a robotic arm;

FIG. 16 is an example of a mechanical connection;

FIG. 16A is a top view of the system of FIG. 16;

FIG. 17 is another example of a mechanical connection;

FIG. 17A is a side view of the system of FIG. 17;

FIG. 17B is another side view of the system of FIG. 17;

FIG. 18 is another example of a mechanical connection;

FIG. 18A is an example of a rotated collimator of the system of FIG. 17;

FIG. 19 is another example of a mechanical connection; and

FIG. 19A is a side view of the system of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following description reference is made to variouscollimators having plates or filters. Both terms are used in the samesense, to describe filters intended to change the intensity of theradiation in a non-uniform manner over the Field of View (FOV), asopposed to filters intended for changing the spectrum of the radiationthroughout the FOV.

Reference is made now to FIG. 1A which presents a typical layout of amultiple frames imaging clinical environment.

X-ray tube 100 generates x-ray radiation 102 directed upward occupying arelatively large solid angle towards a collimator 104. Collimator 104blocks a part of the radiation allowing a smaller solid angle ofradiation to continue in the upward direction, go through bed 108 thatis typically made of material that is relatively transparent to x-rayradiation and through patient 110 who is lying on bed 108. Part of theradiation is absorbed and scattered by the patient and the remainingradiation arrives at the typically round input area 112 of imageintensifier 114. The input area of the image intensifier is typically inthe order of 300 mm in diameter but may vary per the model andtechnology. The image generated by image intensifier 114 is captured bycamera 116, processed by image processor 117 and then displayed onmonitor 118 as image 120. Although the invention is described mainly inreference to the combination of image intensifier 114 and camera 116 itwould be appreciated that both these elements can be replaced by adigital radiography sensor of any technology such as CCD or CMOS flatpanels or other technologies such as Amorphous Silicon withscintillators located at plane 112. One such example is CXDI-50RFAvailable from Canon U.S.A., Inc., Lake Success, N.Y. The term“detector” is used to include any of these technologies, including thecombination of any image intensifier with any camera and including anytype of a flat panel sensor or any other device converting x-ray toelectronic signal.

The terms “area” and “region” are used alternatively in the detaileddescription of the invention and they mean the same and are used assynonyms.

The term “x-ray source” is used to provide a wide interpretation for adevice having x-ray point source that does not necessarily have theshape of a tube. Although the term x-ray tube is used in the examples ofthe invention in convention with common terminology in the art, it isrepresented here that the examples of the invention are not limited to anarrow interpretation of x-ray tube and that any x-ray source can beused in these examples (for example even radioactive material configuredto function as a point source).

Operator 122 is standing by the patient to perform the medical procedurewhile watching image 120.

The operator has a foot-switch 124. When pressing the switch, continuousx-ray radiation (or relatively high frequency pulsed x-ray as explainedbelow) is emitted to provide a cine imaging 120. The intensity of x-rayradiation is typically optimized in a tradeoff of low intensity that isdesired to reduce exposure to the patient and the operator and highintensity radiation that is desired to enable a high quality image 120(high S/N). With low intensity x-ray radiation and thus low exposure ofthe image intensifier input area, the S/N of image 120 might be so lowthat image 120 becomes useless.

Coordinate system 126 is a reference Cartesian coordinate system with Yaxis pointing into the page and X-Y is a plane parallel to planes suchas that of collimator 104 and image intensifier input plane 112.

It is a purpose of the present invention to provide high exposure at theinput area of the image intensifier in the desired one or more ROIs thatprovide therefore a high S/N image there while reducing the exposure ofother sections of the image intensifier area, at the cost of lower imagequality (lower S/N). With this arrangement the operator can see a clearimage in the one or more ROIs and get a good enough image for generalorientation in the rest of the image area. It is also a purpose of thisinvention to provide more complex map of segments in the image whereeach segment results from a different level of x-ray radiation asdesired by the specific application.

According to some embodiments, the x-ray system may include multiplefilament elements to generate multiple and simultaneous X Ray beams, asubset of which may be selected and may be configured to modify thex-ray radiation in order to aim at the desired ROIs in the field of viewaccording to the location of the operator's focus of attention.

According to some embodiments, the x-ray system may include amatrix/array of x ray tubes/sources to generate multiple andsimultaneous X Ray beams, a subset of which may be selected and may beconfigured to modify the x-ray radiation in order to aim at the desiredROIs in the field of view according to the location of the operator'sfocus of attention.

According to some embodiments, the x-ray system may further includerotatable and translatable cathodes and/or anodes to generate multipleand simultaneous X Ray beams, a subset of which may be selected and maybe configured to modify the x-ray radiation in order to aim at thedesired ROIs in the field of view according to the location of theoperator's focus of attention.

An example of a more detailed layout of a multiple frames imagingclinical environment according to the present invention is described inFIG. 1B. Operator 122 presses foot switch 124 to activate the x-ray.Input device 128 provides indication of one or more ROIs. Thisinformation is typically provided relative to monitor 118. Thisinformation, the at least one desired center of ROI, may be provided forexample in terms of (X,Z) coordinates, in the plane of monitor 118,using coordinate system 126. It would be appreciated that in thisexample the plane of monitor 118 and therefore also image 120 areparallel to the (X,Z) plane of coordinate system 126. Other coordinatesystems are possible, including coordinate systems that are bundled tomonitor 118 and rotate with monitor 118 when it is rotated relative tocoordinate system 126.

The data from input 128 is provided to controller 127 which is basicallya computer, such as any PC computer.

Box 150 in FIG. 1B represents a collimator according to the presentinvention, for example, the collimator of FIGS. 4 through 11.

Box 150 can be located under collimator 104, above collimator 104 asshown by numerical reference 150A or instead of collimator 104 (notshown in FIG. 1B). The collimators represented by boxes 150 and 150A arecontrolled by controller 127. X-ray emission is also controlled bycontroller 127, typically through x-ray controller 130. The collimatorpartially blocks radiation, depending on the determined at least onedesired center of ROI (step 2720). Part of the x-rays are absorbed bythe patient 110 (step 2730) and the remaining radiation arrives at theimage intensifier 114 (step 2740). In step 2750 the image is intensifiedand captured by a camera 116 and in step 2760 the captured image istransferred to the image processor 117 and in step 2770 the processedimage is displayed on monitor 120.

Image processor 117 may assume many forms and may be incorporated in thecurrent invention in different ways. In the example of FIG. 1B, imageprocessor 117 includes two main sub units: 117A provides basic imagecorrection such as pixel non-uniformity (dark offset, sensitivity,reconstruction of dead pixels etc), 117C provides image enhancementprocessing (such as noise reduction, un-sharp masking, gamma correctionetc). In conventional systems, the image from sub-unit 117A istransferred for further processing in sub-unit 117C. The sub-units ofimage processor 117 can be supported each by a dedicated hardware butthey can also be logical sub-units that are supported by any hardware.In the example of FIG. 1B the image from camera 116 is corrected byimage processing sub-unit 117A and then transferred to controller 127.Controller 127 processes the image as required from using any of thecollimators represented by box 150 and returns the processed image tosub-unit 117C for image enhancement.

It would be appreciated that the image processing of controller 127 doesnot have to take place in controller 127 and it can be executed by athird sub-unit 117B (not shown in FIG. 1B) located between 117A and117C. Sub-unit 117B can also be only a logical process performedanywhere in image processor 117. It would also be appreciated that x-raycontroller 130 is presented here in the broad sense of systemcontroller. As such it may also communicate with image processor 117 todetermine its operating parameters and receive information as shown bycommunication line 132, It may control image intensifier 114, forexample for zoom parameters (communication line not shown), it maycontrol camera 116 parameters (communication line not shown), it maycontrol the c-arm and bed position (communication line not shown) and itmay control x-ray tube 100 and collimator 104 operation parameters(communication line not shown). There may be a user interface foroperator 122 or other staff members to input requests or any other needsto x-ray controller 130 (not shown).

Physically, part or all of image processor 117, controller 127 and x-raygenerator (the electrical unit that drives x-ray tube 100) may all beincluded in x-ray controller 130. X-ray controller 130 may contain oneor more computers and suitable software to support the requiredfunctionality. An example for such a system with an x-ray controller ismobile c-arm OEC 9900 Elite available from GE OEC Medical Systems, Inc.,Salt Lake City, Utah USA. It would be appreciated that the exemplarysystem is not identical to the system of FIGS. 1B and is only providedas a general example. Some of these features are shown in FIG. 3.Reference is made now to FIG. 2 illustrating an example of an image 120displayed on monitor 118. In this example dashed circle line 204indicates the border between segment 200 of the image and segment 202 ofthe image, both segments constitute the entire image 120. In thisexample it is desired to get a good image quality in segment 200,meaning higher x-ray DPP for segment 200 and it is acceptable to have alower image quality in segment 202, meaning lower DPP for segment 202.

It would be appreciated that the two segments 200 and 202 are providedhere only as one example of an embodiment of the invention that is notlimited to this example and that image 120 can be divided to any set ofsegments by controlling the shape of the apertures in the collimatorsand mode of motion of the collimators. Such examples are provided below.

It would be appreciated that DPP should be interpreted as the x-ray dosedelivered towards a segment representing one pixel of image 120 togenerate the pixel readout value used to construct image 120 (excludingabsorption by the patient or other elements which are not a part of thesystem, such as the hands and tools of the operator).

As explained above, pixels with different DPP per the collimator designand use are normalized to provide a proper display-frame. Normalizationscheme is made in accordance with the x-ray exposure scheme (i.e.,collimator shape, speed and position). Such normalization can be done onthe basis of theoretical parameters.

Collimators according to this invention can be mounted on an x-raysystem as stand-alone or together with another collimator, for example,such that is designed to limit the x-ray to a part of input area 112 ofthe image intensifier. Collimators of the invention and othercollimators may be placed in any order along the x-ray path. The exposedpart of area 112 is the remaining of the superposition of the area ofall the collimators in the path of the x-ray block. In the design ofsuch successive arrangement, the distances of each of the collimatorsfrom the x-ray source and distance to area 112 needs to be consideredwith the geometry of the collimators, as described above, to get thedesired functionality.

In the present example, the at least one ROI becomes the area used forimage optimization. The input device, provides the ROI coordinates ofthe at least one user on the screen. The ROIs are moved to thesecoordinates, with a complementary adjustment of the collimator and theoptimization is made for the image included in the ROIs.

The image may be optimized per the ROIs' content using any of the abovementioned parameters or any other parameter that modifies the displayedvalue of a pixel in the image.

Attention is drawn now to FIG. 3 which presents an exemplary system forcarrying out the invention.

Typically in x-ray systems, an ROI that is centered in image 120 (suchas ROI 200 of FIG. 2) and has a fixed position is used for imageanalysis and for generating parameters to drive x-ray tube 100 andmodify image 120. Parameters such as average value, maximum value andcontrast may be calculated for this area. Such parameters are typicallyused to optimize the x-ray tube operation (such as mA, mAs and KVp).

In this example an input device 127 is used to provide x-ray controller130 with the ROI coordinates of one or more users 122.

The input device can be any input device that affects the positionand/or the shape of the ROI. For example, an eye tracker, a joy-stick, akeyboard, an interactive display, a gesture reading device, a voiceinterpreter or any other suitable device can be used to determinecoordinates relative to image 120, and the ROI position and/or shapechanges according to such input.

According to embodiments of the invention, some of the input devices mayneed a user interface 129.

The user interface can have any display, operated by any computer ortablet, use mouse, trackball or touch-screen, joystick or hand gestureto control the selection of the ROI.

The following examples, demonstrated in FIGS. 4 through 11, presentcollimators for collimating x-ray radiation in x-ray systems comprisinga displayed image of the irradiated area. The systems share thefollowing characteristics:

-   -   A first part of the image represents the ROI: unfiltered        radiation section (100% of the radiation arriving at the        collimator plates)    -   A second part of the image is background, where radiation is        filtered by the collimator plates (100%>radiation≥0 of the        radiation arriving at the collimator plates)    -   The background filter comprises at least three separate filters    -   The background image area comprises at least one point at one        filter area of the image and at least one point at a second        filter area of the image;    -   There is at least one contour, connecting these two points,        wherein, the radiation along the contour encounters essentially        the same filtering characteristics (same total filtering        thickness for example, of filters of a uniform material        composition).

For simplicity, a straight line connecting these two points can beconsidered for the description, but it should be appreciated thatchanging filtration characterization along this line due to changingangle of incidence of the radiation (and therefore the effectivethickness) is particularly considered, in the scope of this invention,as essentially the same filtering characterization. Same is for any ofthe contour or the straight line, in regard to non-uniformity of thefilter thickness, material homogeneity etc., typically present as aresult of manufacturing accuracy limitations, they are all included in“essentially the same” terminology.

This includes also filters that are not at the same height or withouttouching edges etc. They are still coupled but the distance between theedges may change according to the position (incidence angle). This willbe explained in more details in conjunction with FIGS. 12D and 12E.

Also, when using the term “uniform” in reference to filtering, the scopeof uniform includes such tolerances as described above.

Essentially non-overlapping filters means a design that is intended tosupport the above system characteristics in at least most of the imagearea. A small overlapping that, for example results in extra filteringalong overlapping edges of two adjacent filters would still be includedin “essentially non-overlapping”

Reference is made now to FIG. 4 providing an exemplary collimator 4500according to the present invention.

Collimator 4500 comprises four plates 4501, 4502, 4503 and 4504 that areopaque or partially transparent to x-ray. In this example we shallassume that each such plate transmits 10% of beam 106 but it would beappreciated that other transmission levels may be contemplated. Plates4501, 4502, 4503 and 4504 can be made from any suitable material,considering the desired effect of the spectral distribution of thetransmitted x-ray beam. For example, copper or aluminum plates can beused.

Dashed circle 106A (FIG. 4A) represents x-ray cone 106 cross section atgenerally the plane of collimator 4500. Except for a rectangular shapedx-ray beam portion 3510 (FIG. 4A), the rest of the beam intensity isreduced due to plates 4501, 4502, 4503 and 4504.

Eight motors can move plates 4501, 4502, 4503 and 4504 as explainedbelow. The components of the motorizing elements are detailed inreference to plate 4501. The other 3 plates' mechanisms are analogous.

Motor 4501A drives screw 4501C that moves nut 4501E. Nut 4501E isconnected to plate 4501, therefore enables plate 4501 to move in thedirections of arrow 4501F.

Motor 4501B drives screw 4501D that moves nut 4501E. Nut 4501E isconnected to plate 4501 therefore enables plate 4501 to move indirections of arrow 4501G. Hence, each plate can move as indicated bydual-head arrows for each plate, independently of the other plates. Anexample of possible arrangement of nut 4501E is shown in FIG. 4.1. Rails4505A may be used to support the plates and enable motion. Motors 4501Aand 4501B slide freely on the rails 4505A according to the mentioneddirections.

It would be appreciated that the specific motion mechanism describedherein is provided to explain the invention and that the scope of theinvention is not limited to this motion mechanism.

To create a rectangular ROI each one of two adjacent edges of a filter(plate) is parallel and in contact with the edge of a neighboring filteras demonstrated in FIG. 4.

The collimator 4500 is based on “active coupling”, meaning thecontroller of the motors has to ensure coupling of the plates wherecoupling of two plates means they are in contact along at least a partof an edge.

As mentioned above, each plate is able to move independently but inorder to prevent radiation penetration between the plates the controllerensures that when a plate moves in direction perpendicular to a couplingline, the adjacent plate coupled along this line moves with it and thuscoupling is maintained. Namely, when one motor needs to be moved, thecontroller may move other motors as well, to maintain plates coupling.

It would be appreciated that coupling is not required at all times andit is typically preferred to have the coupling at least when radiationis turned on.

It is appreciated that a circular image/circular cone shape x-ray beamis only an example. The x-ray beam and the image may be rectangular orany other shape, depending on the c-arm and collimator setup.

In the example of FIG. 4A aperture 3512 is in the region of beam 106 (asshown by the beam cross section 106A) and has a certain size dictated bythe required ROI. FIG. 4A demonstrates an adjustment of plates 4501,4502, 4503 and 4504 in order to create the required aperture forproviding radiation to the ROI that is different from the ROI exampleshape of FIG. 4.

With this example of collimator 4500 therefore ROI 3602 of image 120(FIG. 5) cannot only be moved across the area of image 120 to thedesired location but also the size and aspect ratio of the ROI can bechanged as desired, to compensate for zoom in image intensifier 114(FIG. 1A) or for other reasons.

Reference is made now to FIG. 5, illustrating the x-ray intensitydistribution in different areas of image 120 when the image ROI 3602 isin the position resulting from mechanical ROI 3512 presented in FIG. 4A.In this example there is no object (patient) between collimator 4500 andinput area 112 so, ideally, without additional conventional collimatorblocking radiation, the x-ray radiation over input area 112, outside ofthe ROI, would be uniform (up to specific system inherent uniformitylimitations). In this example, as a result of collimator 4500 the areaof image 120 is divided into two intensity areas: 3602, the ROI, wherethe original 100% intensity is and 3604A where the intensity is 10% ofthat at the ROI.

The above described methods to correct background are fully applicableto correct the background 3604A of the present example.

It would be appreciated therefore that the current example can be usedtogether with the above described correction methods.

Reference is made now to FIG. 6 providing an example of collimator 4700according to the present invention.

Collimator 4700 uses four motors instead of the eight motors used in theconfiguration of FIG. 4.

The components of the motorizing elements are detailed in reference toplate 4701. The other 3 plates' mechanisms are analogous.

Motor 4701A drives screw 4701B that moves nut 4701C. Nut 4701C isconnected to plate 4701, therefore enables plate 4701 to move in thedirections of arrow 4701D.

An “L” shaped coupler 4705 connects plates 4701 and 4704 wherein nut4701C slides on the coupler side 4705A and plate 4704 is fixedlyconnected to the other side 4705B of the coupler via a connector 4706.

Therefore, as plate 4701 moves in the directions of arrow 4701D, plate4704 moves with it in the same direction but in order to move in thedirections of arrow 4701E, plate 4702 moves and moves plate 4701 withit.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate.

The collimator 4700 is based on “passive coupling” meaning the “L”shaped couplers ensure coupling of the plates by forcing two adjacentedges of neighboring plates to maintain their relative positions bysliding along each other. The four motors slide freely on the rails4505B according to the mentioned directions.

It would be appreciated that some of the plates may be movable by onemotor and a coupler and some plates may be movable by two motors.

In that case an “active coupling” is needed in addition to the “passivecoupling”.

It would be appreciated that the specific motion mechanism describedherein is provided to explain the invention and that the scope of theinvention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter(plate) is parallel and in contact with the edge of a neighboringfilter.

Reference is made now to FIG. 6A.

FIG. 6A demonstrates an adjustment of plates 4701, 4702, 4703 and 4704in order to create the aperture for providing radiation to the ROI.

With this example of collimator 4700 therefore the ROI of image 120 cannot only be moved across the area of image 120 to the desired locationbut also the size and aspect ratio of the ROI can be changed as desired,to compensate for zoom in image intensifier 114 or for other reasons.

Reference is made now to FIG. 7 providing an example of collimator 4800of the present invention.

Collimator 4800 also uses four motors instead of eight.

The components of the motorizing elements are detailed in reference toplate 4801. The other 3 plates' mechanisms are analogous.

Motor 4801A drives screw 4801B that moves nut 4801C. Nut 4801C isconnected to plate 4801 therefore enables plate 4801 to move in thedirections of arrow 4801D.

A “U” shaped coupler 4805 connects plates 4801 and 4804 wherein nut4801C slides on the coupler side 4805A and nut 4804A slides on thecoupler side 4805B. The connector 4806 is fixedly connected to the rail4505C and allows the coupler to slide through it.

The “U” shaped coupler dictates the motion limitations and ensuresplates' coupling.

Therefore, as plate 4801 moves in the directions of arrow 4801D, plate4804 moves with it in the same direction but in order to move in thedirections of arrow 4801E, plate 4802 moves and moves plate 4801 withit.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate.

The collimator 4800 is based on “passive coupling” meaning the “U”shaped coupler ensures coupling of the plates by forcing two adjacentedges of neighboring plates to maintain their relative positions bysliding along each other. The motors slide freely on the rails 4505Caccording to the mentioned directions. It would be appreciated that someof the plates may be movable by one motor and a coupler and some platesmay be movable by two motors.

In that case an “active coupling” is needed in addition to the “passivecoupling”. It would be appreciated that the specific motion mechanismdescribed herein is provided to explain the invention and that the scopeof the invention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter(plate) is parallel and in contact with the edge of a neighboringfilter.

Reference is made now to FIG. 7A.

In the example of FIG. 7A aperture 3512 is at the region of beam 106 (asshown by the beam cross section 106A) and it has a certain size.

FIG. 7A demonstrates an adjustment of plates 4801, 4802, 4803 and 4804in order to create the aperture for providing radiation to the ROI.

With this example of collimator 4800 therefore the ROI of image 120 cannot only be moved across the area of image 120 to the desired locationbut also the size and aspect ratio of the ROI can be changed as desired,to compensate for zoom in image intensifier 114 or for other reasons.

Reference is made now to FIG. 11 providing an example of collimator 5400of the present invention.

Collimator 5400 also uses four motors instead of eight.

The components of the motorizing elements are detailed in reference toplate 5401. The other 3 plates' mechanisms are analogous.

Motor 5401A moves on rail 4505G and connects plates 5401 and 5402 viacouplers 5402A and 5402B and nuts 5401B and 5401C respectively, therebyenabling plate 5401 to move in the directions of arrow 5401D.

The nuts 5401B and 5401C slide freely on the couplers 5402A and 5402Brespectively. The couplers 5402A and 5402B dictate the motionlimitations and ensure plates' coupling.

Therefore, as plate 5401 moves in the directions of arrow 5401D, plate5402 moves with it in the same direction but in order to move indirections of arrow 5401E, plate 5404 moves and moves plate 5401 withit.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate.

The collimator 5400 is based on “passive coupling” meaning the couplers5402A and 5402B ensure coupling of the plates by forcing two adjacentedges of neighbor filters to maintain the distance between them bysliding along each other.

The motors slide on the rails 4505G according to the mentioneddirections.

It would be appreciated that the specific motion mechanism describedherein is provided to explain the invention and that the scope of theinvention is not limited to this motion mechanism.

To create a rectangular ROI each of two adjacent edges of a filter(plate) is parallel and in contact with the edge of a neighboringfilter.

Reference is made now to FIG. 11A.

In the example of FIG. 11A aperture 3512 is at the region of beam 106(as shown by the beam cross section 106A) and it has a certain size.

FIG. 11A demonstrates an adjustment of plates 5401, 5402, 5403 and 5404in order to create the aperture for providing radiation to the ROI.

With this example of collimator 5400 therefore the ROI of image 120 cannot only be moved across the area of image 120 to the desired locationbut also the size and aspect ratio of the ROI can be changed as desired,to compensate for zoom in image intensifier 114 or for other reasons.

Reference is made now to FIG. 8 providing an example of collimator 4900of the present invention.

Collimator 4900 has three filters (plates) and uses three motors.

The components of the motorizing elements are detailed in reference toplate 4901. The other two plates' mechanisms are analogous.

Motor 4901A drives screw 4901B that moves nut 4901C. Nut 4901C isconnected to plate 4901 therefore enables plate 4901 to move in thedirections of arrow 4901F.

A “U” shaped coupler 4905 connects plates 4901 and 4902 wherein nut4901E slides on the coupler side 4905A and nut 4902A slides on thecoupler side 4905B.

The “U” shaped coupler dictates the motion limitations and ensureplates' coupling.

Therefore, as plate 4901 moves in directions of arrow 4901F, plate 4903moves with it in the directions of arrow 4903A but in order to move inthe directions of arrow 4901D, plate 4902 moves in the directions ofarrow 4903A and moves plate 4901 with it.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate. Therefore, when thecontroller moves one motor, other motors may need to move.

The collimator 4900 is based on “passive coupling” meaning the couplers5402A and 5402B ensure coupling of the plates by forcing two adjacentedges of neighbor filters to maintain the distance between them bysliding along each other.

The motors slide freely on the rails 4505D according to the mentioneddirections. It would be appreciated that some of the plates may bemovable by one motor and a coupler and some plates may be movable by twomotors.

In that case an “active coupling” is needed in addition to the “passivecoupling”. It would be appreciated that the specific motion mechanismdescribed herein is provided to explain the invention and that the scopeof the invention is not limited to this motion mechanism.

Reference is made now to FIG. 8A.

FIG. 8A demonstrates an adjustment of plates 4901, 4902 and 4903 inorder to create the aperture for providing radiation to the ROI.

With this example of collimator 4900 therefore the ROI of image 120 cannot only be moved across the area of image 120 to the desired locationbut also the size and aspect ratio of the ROI can be changed as desired,to compensate for zoom in image intensifier 114 or for other reasons.

Reference is made now to FIG. 9 providing an example of collimator 5000of the present invention.

Collimator 5000 has five plates (filters) and uses five motors.

The components of the motorizing elements are detailed in reference toplate 5001. The other four plates' mechanisms are analogous.

Motor 5001A drives screw 5001B that moves nut 5001C. Nut 5001C isconnected to plate 5001 thus enabling plate 5001 to move in thedirections of arrow 5001D. A “U” shaped coupler 5006 connects plates5001 and 5002 wherein nut 5001E slides on the coupler side 5006A and nut5002A slides on the coupler side 5006B.

The “U” shaped coupler dictates the motion limitations and ensureplates' coupling.

Therefore, as plate 5001 moves in directions of arrow 5001D, plate 5002moves with it in the directions of arrow 5002B but in order to move inthe directions of arrow 5001F, plate 5005 moves and moves plate 5001with it.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate. Therefore, when thecontroller moves one motor, other motors may need to move.

The collimator 5000 is based on “passive coupling” meaning the “U”shaped couplers ensure coupling of the plates by forcing two adjacentedges of neighbor filters to maintain the distance between them bysliding along each other.

The motors slide freely on the rails 4505E according to the mentioneddirections. It would be appreciated that some of the plates may bemovable by one motor and a coupler and some plates may be movable by twomotors.

In that case an “active coupling” is needed in addition to the “passivecoupling”.

It would be appreciated that the specific motion mechanism describedherein is provided to explain the invention and that the scope of theinvention is not limited to this motion mechanism.

Reference is made now to FIG. 9A through 9C.

In the examples of FIGS. 9A, 9B and 9C aperture 3512 is at the region ofbeam 106 (as shown by the beam cross section 106A) and it has a certainsize. FIG. 9A demonstrates an adjustment of plates 5001, 5002, 5003,5004 and 5005 in order to create a specific needed pentagonal ROI.

FIG. 9B demonstrates an adjustment of plates 5001, 5002, 5003, 5004 and5005 in order to create a specific needed quadrangular ROI.

FIG. 9C demonstrates an adjustment of plates 5001, 5002, 5003, 5004 and5005 in order to create a specific needed triangular ROI.

Reference is made now to FIG. 10 providing an example of collimator 5100of the present invention.

Collimator 5100 has twelve plates (filters) and uses twelve motors.

FIG. 10A shows an enlargement of the components of the motorizingelements that are detailed in reference to plate 5101. The other elevenplates' mechanisms are analogous.

Motor 5101A drives screw 5101B that moves nut 5101C. Nut 5101C isconnected to plate 5101 thus enabling plate 5101 to move in thedirections of arrow 5101D. A “U” shaped coupler 5106 connects plates5101 and 5102 wherein nut 5101E slides on the coupler side 5106A and nut5102A slides on the coupler side 5106B.

The “U” shaped coupler dictates the motion limitations and ensuresplates' coupling.

Therefore, as plate 5101 moves in the directions of arrow 5101D, plate5102 moves with it in the same direction but in order to move indirections of arrow 5101F, plate 5112 moves and moves plate 5101 withit.

Hence, according to this configuration, a single plate cannot movewithout causing movement of another plate. Therefore, when thecontroller moves one motor, other motors may need to move.

The collimator 5100 is based on “passive coupling” meaning the “U”shaped couplers ensure coupling of the plates by forcing two adjacentedges of neighbor filters to maintain the distance between them bysliding along each other.

The motors slide freely on the rails 4505F according to the mentioneddirections. It would be appreciated that some of the plates may bemovable by one motor and a coupler and some plates may be movable by twomotors.

In that case an “active coupling” is needed in addition to the “passivecoupling”. It would be appreciated that the specific motion mechanismdescribed herein is provided to explain the invention and that the scopeof the invention is not limited to this motion mechanism.

Reference is made now to FIGS. 10B and 10C

FIGS. 10B and 10C demonstrate an adjustment of plates 5101 through 5112in order to create a specific ROI such as 3512B and 3512C.

The concept is expandable to any number of plates >2.

All the examples shown can also be placed on a rotatable and/ordisplaceable mechanism in x-y plane. Rotation is particularly useful forsolutions with relatively small number of plates (such as 3, 4 and 5).12 plates virtually eliminate the need for rotation.

A problem that may occur while using the “essentially non-overlappingfilters” collimators aforementioned is a penetration of X-Ray radiationbetween the collimator plates.

FIG. 12A demonstrates the use of “straight edge” plates with radiationbeam 5320 penetrating the filtering layer through a small gap betweenplates 5322 and 5324. This makes the line along which the two platesmeet visible on the image as illustrated on resulting image 5326.

FIGS. 12B and 12C offer two solutions to the problem.

FIG. 12B demonstrates the use of “V shaped edge” plate with a negativeor reversed V edge plate fitting each other so that ray 5320A cannotpass through the line of plates contact without being filtered. Theresulting image 5326A without the effect of radiation un-intendedpenetration is shown.

FIG. 12C demonstrates the use of “tapered edge” plates and the resultingimage.

Other edge shapes are considered, such as arcuate, concave, convex,contoured, or stepped, or any complementary, mating edge shape thateffectively prevent line-of sight through the abutting plates along theprimary direction of beam travel.

FIGS. 12D and 12E provide another example for the coupling concept ofthe present invention. For this example, plates 5302 and 5304 of FIG.12C are used. Unlike FIG. 12C where plates 5302 and 5304 are at the sameplane, in FIGS. 12D and 12E plates 5302 and 5304 are not in the sameplane. Plate 5304 is further away from radiation source 5306, indirection perpendicular to the planes of plates 5302 and 5304.

In FIG. 12D plates 5302 and 5304 are shown to the right of radiationsource 5306. The horizontal distance between plates 5302 and 5304 is setso that radiation rays passing through each of the filters and in thezone including both filters experience essentially the same filtering.In this example ray 5311 is passing through plate 5302 only, ray 5313 ispassing through plate 5304 only and ray 5312 passes through both plates5302 and 5304. The horizontal distance between plates 5302 and 5304 isset so that all 3 rays experience essentially the same thickness offiltering.

In FIG. 12E plates 5302 and 5304 are shown to the left of radiationsource 5306. Ray 5311A passes through plate 5302 only, ray 5313A passesthrough plate 5304 only and ray 5312A passes through both plates 5302and 5304. The horizontal distance between plates 5302 and 5304 is set sothat all 3 rays experience essentially the same thickness of filtering.Note that the horizontal distance between plates 5302 and 5304 in FIG.12E is smaller than in FIG. 12D. This is because the change in the angleof incidence of the radiation rays. This demonstrates the concept ofplates that are “coupled” in this invention. They are coupled in thesense of a constraint, requiring that the distance between the platesserves the purpose of essentially uniform filtering on a transition fromone plate to another and not, for example, mechanical fixed distance(although mechanical fixed distance can serve as the desired couplingimplementation for certain mechanical designs). It would be appreciatedthat the specific examples described here are provided to explain theinvention and that the scope of the invention is not limited to thesespecific solutions.

It would be appreciated that although the above was described inreference to an image intensifier it is applicable to any detector,including a flat panel detector. The geometry of the detector, the zoomarea and the ROI can be of a mixed nature and do not need to be of thesame nature (i.e. circular or rectangular or another geometry).

It would be appreciated that throughout the description when, forexample, the term aperture is used in the context of elongated aperture,the intention is to an elongated aperture.

It would be appreciated that “partially transparent” and “attenuating”are equivalent and the role of such a term is dependent on the amount oftransparency or attenuation. In the above description the role of suchterms is provided by the context of the description with specific valueexamples where needed. The structure examples provided in thisdisclosure can be implemented with different degrees of transparency tox-ray (or, equivalently, with different degrees of attenuation ofx-ray), as preferred for specific implementations. As such they can behighly transitive to x-ray (low attenuation) or poorly transmisive tox-ray (high attenuation). High attenuation also refers to “x-rayblocking” terms since x-ray cannot be 100% blocked and “blocking” isused in the field of the invention to indicate high attenuation.

FIG. 13 shows an exemplary user interface which may be implemented aspart of a control application running on an electronic device having aninteractive display, such as a tablet, a monitor or a smartphone. Theapplication communicates with the controller 132 and displays thecaptured and corrected x-ray image.

The user uses four sliders 10201 to determine ROI 10210 size andlocation according to the area encodes by border lines 10201A, arotation button 10202 to determine a rotation direction of the selectedROI (clockwise or anticlockwise) and initiates a rotation of the ROIaccordingly until released, a displacement button 10203 for moving theselected ROI without changing its size and orientation and an optional“GO” button 10204 for implementing the actual motion of the collimatorplates according to the indicated location, orientation and aperturesize.

In the absence of a “GO” button, the plates' motion could starts eachtime the buttons are released or, in another example, after apredetermined time period with no changes in the interface setup.

FIG. 13A is another example of a user interface. In order to select thewanted ROI the user marks any enclosing shape such as shape 10205 on thescreen and the collimator plates are arranged in a position where theyform an aperture that best encloses the shape. “GO” button 10204 isoptional.

In the absence of a “GO” button, the plates' motion could starts eachtime the user stops drawing, or in another example, after the userremoves his finger or drawing pen from a touch screen, or, in anotherexample, after a predetermined time period with no changes in theinterface setup.

FIG. 13B is another example that is implemented on the same userinterface as in FIG. 13A. In order to select the wanted ROI the usermarks any shape such as line 10206 on the screen and the collimatorplates are arranged in a position where they form an aperture that bestencloses the shape.

“GO” button 10204 is optional.

In the absence of a “GO” button, the plates' motion could starts eachtime the user stops drawing, or in another example, after the userremoves his finger or drawing pen from a touch screen, or, in anotherexample, after a predetermined time period with no changes in theinterface setup.

FIG. 13C is another example that is implemented on the same userinterface as in FIG. 13A. In order to select the wanted ROI the usermarks more than one shape such as lines 10207A and 10207B on the screenand the collimator plates are arranged in a position where they form anaperture that best encloses the shapes.

“GO” button 10204 is optional.

In the absence of a “GO” button, the plates' motion could start eachtime the user stops drawing a shape segment. Alternatively, the plates'motion could start after a predetermined time period with no changes inthe interface setup. If time≤time period—shape is not completed(wait forthe user to add new segment to the existing segments). If time>timeperiod—the drawing is finished and motion of ROI is engaged.

FIG. 13D is another example that is implemented on the same userinterface as in FIG. 13A. In order to select the wanted ROI the usermarks more than one shape such as lines 10207A and 10207B on the screenand the collimator plates are arranged and rotated in a position wherethey form the smallest aperture that encloses the shapes. In thisexample the aperture shape is fixed.

FIG. 13E is another example that is implemented on the same userinterface as in FIG. 13A. In order to select the wanted ROI the usermarks more than one shape such as lines 10207A and 10207B on the screenand the collimator plates are arranged and rotated in a position wherethey form the smallest aperture that best encloses the shapes. In thisexample the aperture shape may be changed. FIG. 13F is another examplethat is implemented on the same user interface as in FIG. 13A. In orderto select the wanted ROI the user marks any shape such as line 10206 onthe screen and the collimator plates are arranged in a position wherethey form an aperture that encloses the shape.

When an additional point 10220 is added outside the ROI, the nearestedge to that point could move in parallel to its direction to that pointso that calculated ROI 10212 changes to ROI 10222. In this example theaperture shape is fixed.

FIG. 13G is another example, if the of the point 10220A to two nearestedges of the ROI is below some determined value, the corner where thesetwo lines meet could move to the marked point so that calculated ROI10212 changes to ROI 10222A. In this example the aperture shape may bechanged.

ROI 10212 borders could be automatically calculated and set in a varietyof methods including:

-   -   1. Closing on the enclosed area 10214 so that two of the ROI        edges are horizontal and located at maximum Y and minimum Y of        area 10214 (in reference to coordinate system 10216 in FIG.        13A-13C) at the top and at the bottom of area 10214 and two of        the ROI edges are vertical and located at maximum X and minimum        X of the border of area 10214 at the left and at right of area        10214.    -   2. Same method as (1) but including the marking lines that are        outside of enclosed area 10214.    -   3. The method of either (1) or (2) and also rotating the        rectangular ROI to an angle that encloses a smaller area. This        is demonstrated in FIG. 13D where ROI 10214 is rotated and each        of the edges of the ROI is set, relative to coordinate system        10216A that is now rotated, for reference, at the same angle ROI        10214 is rotated. Also here the edges parallel to the Y        direction enclose on the combined shape of 10207A and 10207B in        a position of maximum X and minimum X of the combined shape and        the edges parallel to the X axis direction enclose on the        combined shape of 10207A and 10207B in a position of maximum Y        and minimum Y of the combined shape so that ROI 10214 has        smaller area than ROI 10212 of FIG. 13C for the same shape.        Different criteria may be involved in determining the ROI shape,        size and angle. For example:        -   a. Minimal area could be one criterion for setting the ROI            angle and borders as described above.        -   b. Aspect ratio could be another criterion to set the ROI            angle and borders as described above.        -   c. Minimal ROI dimension could also be used as a criterion            for calculating the desired ROI.        -   d. An area or dimension factor criterion could also be used            to calculate the desired ROI. For example, the calculated            area to enclose with the ROI can be a certain percentage of            the minimal area. In another example at least one calculated            dimensions of the ROI can be changed by a certain            percentage. Such changes could also be done using an            additive value (positive or negative) instead or with a            percentage value.        -   e. A criterion using a percentage of the entire field of            view could be used to calculate the desired ROI. For            example, such a criterion could require that the ROI area            would be 15% of the area of the field of view. In another            example the area of the ROI could include a certain amount            of pixels of the image.        -   f. A constraint input by the user could be used also. For            example, after setting ROI according to any of the above            methods, the user could mark a point outside the ROI (10220            in FIG. 13F) and the nearest edge to that point could move            in parallel to its direction to that point so that            calculated ROI 10212 changes to ROI 10222 (FIG. 13F). In            another example, if the difference of the point distances to            two nearest edges of the ROI is below some determined value            (10220A in FIG. 13G), the corner where these two lines meet            could move to the marked point so that calculated ROI 10212            changes to ROI 10222A (FIG. 13G).        -   g. The constraints of section (f) above could also be            introduced by any of touching at least one of the line            images of the ROI and dragging it perpendicularly to its            direction and touching at least one of the corner images of            the ROI and dragging it in any direction. Such touching and            dragging could be done using any input device such as a            finger on a touch screen or a mouse of a computer.        -   h. A combination of any of the above criteria could be used            to calculate the desired ROI. For example, An ROI with a            minimal area could be calculated, then the aspect ratio            criterion could be employed to increase the smaller size of            the ROI until the aspect ratio limitation is satisfied.            Then, if the resulting area is still below any area            criterion, the ROI could be increased (maintaining the            aspect ratio, angle and center) until the area criterion is            satisfied. Following that the user can mark a point near an            edge, inside the ROI, and the edge moves to that point            (overriding the aspect ratio and area criteria.    -   4. The method of either (1), (2) or (3) and also changing from        rectangle to any 4-edges shape enclosing the minimal area, as        per the example of ROI 10218 of FIG. 13E.    -   5. Closing on the drawn area 10206 so that two of the ROI edges        are horizontal and tangent to the border of 10206 area at the        top and at the bottom of area 10206 and two of the ROI edges are        vertical and tangent to the border of 10206 area at the left and        at right of area 10206.    -   6. Closing on the drawn area comprising more than one drawing        10207A and 10207B so that two of the ROI edges are horizontal        and tangent to the border of 10207A and 10207B area at the top        and at the bottom of drawings 10207A and 10207B and two of the        ROI edges are vertical and tangent to the border of 10207A and        10207B area at the left and at right of drawings 10207A and        10207B.    -   7. The method of either (5) or (6) and also rotating the        rectangular ROI to an angle that encloses the minimal area.    -   8. The method of either (5), (6) or (7) and also changing from        rectangle to any 4-edge shape so as to enclose the minimal area.

In the example of FIGS. 13A-13D and 13F an enclosing rectangle is shown,which corresponds to a rectangular aperture such as shown in conjunctionwith the collimator of FIGS. 4-7, as will be explained below. In theexample of FIGS. 13E and 13G an enclosing quadrilateral is shown, whichcorresponds to a quadrilateral aperture such as shown in conjunctionwith an embodiment of the collimator of FIG. 8-10

The user interface can be operated using touch screen or any other inputdevice such as a computer mouse.

Both user interface options (FIGS. 13 and 13A) may be active at the sametime and the user may select the most appropriate one.

According to another embodiment of the present invention, any collimatordescribed herein and any other existing or future collimator may beadded to an existing multiple frame imaging system as a retrofit,mechanically connected with the C-Arm and mounted between the existingcollimator and the patient. FIG. 14 depicts schematically such a system5500 comprising an X-ray source 5510, an original collimator 5515, anadditional collimator 5520 according to the present invention, a patient5530, a C-Arm 5535, a detector 5540, an X-Ray controller 5550, an X-Rayoperating pedal 5560, an exemplary user interface device joy stick 5570and a display 5580.

The new system controller 5565 is connected with the detector 5540 toreceiver therefrom detected images, image process them as describedabove in conjunction with the various embodiments, displays thecorrected image on the display 5580 and controls the collimator 5520according to inputs from the joy stick (or tablet or any other userinterface device capable of indicating a required ROI relative to adisplayed image).

Display 5580 may display the image obtained through both collimatorswithout image correction, the image obtained through both collimatorswith image correction and the image obtained through the originalcollimator only.

According to embodiments of the invention, the user interface device mayprovide selection between the two collimators to determine whichcollimator is currently addressed. Furthermore, when the originalcollimator is selected for operation/activation the newly insertedcollimator would translate in parallel with the X-Ray detector plane andmove out of the X Ray beam pathway so that not to effect the beam.

The additional collimator 5520 according to the present invention may beconnected to the original collimator 5515, or to the radiation tube orto the c-arm by mechanical or other connection means as will beexplained bellow in FIGS. 16-19A.

FIG. 15 is another embodiment of the system of FIG. 14 according to thepresent invention. The additional collimator 5520 may also be driven bya robotic arm 5610 such as for example in coordination with the originalcollimator 5515, such that the new collimator moves and functions whilebeing mechanically supported on its own base without necessarily beingmechanically attached to any moving section of the original X-raysystem. Such robotic arm will use electronic sensors and controllers toprovide accurate tracking motion as needed to perform the collimationfunction of the new collimator which is attached to the endeffector/gripper/hand of the robot.

The “robotic arm” may be controlled by use of:

-   -   1. Multiple sensors such as optical, magnetic or others that        ensure tracking and coordination with the original collimator        and X Ray system.    -   2. The robot controller 5620 communicates directly with (or in        some cases may be embedded within) the C-ARM motion controller        5630.

As mentioned above the additional collimator 5520 according to thepresent invention may be connected to the original collimator 5515, orto the radiation tube or to the c-arm by mechanical or other connectionmeans. FIG. 16 is an example of such mechanical connection. Collimator5520 is steadily mounted via adapter 5700 to the c-arm 5710 by screws,glue, welding, etc. 5720 that ensure coupling of the adapter and thecollimator.

FIG. 16A is a top view of the system of FIG. 16.

FIG. 17 is another example of a mechanical connection. Collimator 5520is steadily mounted via adapter 5810 to the original collimator cover orto the radiation tube cover 5820 by screws, glue, welding, etc. 5830that ensure coupling of the collimator.

FIGS. 17A and 17B are side views of the system of FIG. 17.

FIG. 18 is another example of a mechanical connection. Collimator 5520is steadily mounted via adapter 5910 to the original collimator cover orto the radiation tube cover 5920 by screws, glue, welding, etc. 5930that ensure coupling of the collimator. The adapter additionallycomprises a rotation unit comprising a motor 5940 and a slew bearing5950. After the collimator 5520 is mounted, it can be rotated using thisrotation unit. Sensors 5960 may be placed in each corner of thecollimator 5520 (two not shown) in order to prevent collision, forexample, with the c-arm.

FIG. 18A is an example of the system of FIG. 18 when collimator 5520 isrotated.

FIG. 19 is another example of a mechanical connection. Collimator 5520is steadily mounted via adapter 6010 to the c-arm cabinet 6020. Theadapter may be connected anywhere on the c-arm cabinet or rest on wheelson the floor, typically next to cabinet 6020 or the cabinet wheels (notshown).

If it is coupled to the cabinet, it travels with it. The motions ofadaptor 6010 components are the same as the c-arm analog components indirections of dual head arrows 6030-6060 (shown in FIG. 19A).

FIG. 19A is a side view of the system of FIG. 19 with direction dualhead arrows 6030-6050.

For example, component 6031 adaptor 6010 is coupled to c-arm component6032 and whenever c-arm part 6032 moves, adaptor component 6031 followsit and maintains its' position relative to c-arm component 6032. In thesame way, each component of the c-arm “arm” that holds collimator 5920has the analog component in adaptor 6010 that is coupled to it, andmoves with it maintaining the relative position.

It would be appreciated by those skilled in the art that the abovedescribed methods and technologies are not limited to the configurationsand methods mentioned herein above as examples. These are provided asexamples and other configurations and methods can be used to optimizefinal result, depending on the specific design and the set oftechnologies implemented in the production of the design, includingcombinations of various embodiments described separately.

The herein above embodiments are described in a way of example only anddo not specify a limited scope of the invention.

The scope of the invention is defined solely by the claims providedherein below.

The invention claimed is:
 1. A collimator said collimator comprising: atleast three plates adapted to be mounted generally parallel to adetector input surface plane, said at least three plates forming a fullytransparent gap therebetween, wherein each plate comprises a first edgeforming a side of the gap and a second edge adjacent said first edge incontact with the first edge of a neighboring plate; each plate may bedefined as a first plate, said first plate is configured to move in afirst direction relative to said first plate's first edge and aneighboring plate to said first plate is configured to move in a seconddirection relative to said neighboring plate's first edge, said firstdirection relative to said first plate's first edge is different fromsaid second direction relative to said neighboring plate's first edge;at least two plates are arranged so that there is a contour on an imageconnecting a first point at a first filter area of the image and asecond point at a second filter area of the image; and wherein filteringof rays along the contour is essentially uniform.
 2. A multiple frameimaging system comprising: a radiation source; a detector having aninput area; a monitor configured to display detected images; means fordetermining at least one region of interest of an object on a displayedimage; and a collimator according to claim 1, comprising means formodifying said radiation according to said at least one region ofinterest.
 3. The system of claim 2, further comprising: an imageprocessing unit connected between said detector and said monitor, saidimage processing unit configured to optimize a detected image displayedon said monitor according to at least one image part in said at leastone region of interest.
 4. The system of claim 3, wherein said means fordetermining the at least one region of interest comprise a graphicaluser interface.
 5. The system of claim 4, wherein said graphical userinterface comprises means for displaying detected images and means fordetermining shape and location of the at least one region of interest.6. The system of claim 5, wherein said means for determining the atleast one region of interest shape and location comprise sliders.
 7. Thesystem of claim 5, wherein said graphical user interface furthercomprises means for rotating said determined at least one region ofinterest.
 8. The system of claim 5, wherein said means for determiningthe at least one region of interest shape and location comprise drawingtools.
 9. The system of claim 8, wherein said drawing tools areconfigured to mark an enclosing shape around at least one area.
 10. Thesystem of claim 8, wherein said drawing tools are configured to mark atleast one line; and wherein said means for determining the shape andlocation the at least one region of interest comprises means forcalculating an enclosing shape around said at least one line.
 11. Amethod of controlling a display shape of a region of interest in animage of an x-ray irradiated area, comprising: providing a multipleframe imaging system comprising: an x-ray source; a detector having aninput area; and a collimator comprising means for projecting at leastone region of interest on a selected fraction of said input area exposedby said x-ray source; said collimator comprising at least threeessentially non-overlapping plates mounted in a plane generally parallelto a detector input surface plane, said plates forming a fullytransparent gap therebetween, wherein each plate comprises a first edgeforming a side of the gap and a second edge adjacent to said first edgein contact with the first edge of a neighboring plate; and determiningat least one location and shape of an exposed area image on saiddetector input area by moving a first plates in said plane in a firstdirection relative to said first plate's first edge and moving theneighboring plate in a second direction relative to said neighboringplate's first edge, wherein said first direction relative to said firstplate's first edge is different from said second direction relative tosaid neighboring plate's first edge.
 12. The method of claim 11, whereinsaid determining the shape and location of the at least one region ofinterest comprises moving sliders.
 13. The method of claim 12, whereinsaid determining the shape and location of the at least one region ofinterest comprises drawing at least one line; and calculating anenclosing shape around said at least one line.
 14. The method of claim12, further including the step of rotating said determined at least oneregion of interest.
 15. The method of claim 11, wherein the multipleframe imagining system further comprises a graphical user interface fordetermining the at least one region of interest.
 16. The method of claim15, further comprising the step of using the graphical user interface todisplay detected images and determine shape and location of the at leastone region of interest.
 17. The method of claim 12, wherein saiddetermining the shape and location of the at least one region ofinterest comprises drawing an enclosing shape around at least one area.